Conclusion & Future Perspective
The clinical efficacy of SCIT (typical shots) is well established for both rhinitis and asthma. SLIT (sublingual drops) has also been validated in regards to rhinitis and asthma. Two recent meta-analyses in children showed that sublingual delivery of allergen vaccination constitutes a safe and effective alternative to the injectable route to reduce allergic respiratory symptoms and drug intake. Assessment of possible long-term benefits, including long-term disease remissions, suppression of new allergic sensitizations, and reduction of progression from rhinitis to asthma in children, as has been shown for the subcutaneous route, are future requirements for “proof” of benefits for sublingual drops.
The immunological effects of SLIT and how these relate to clinical efficacy are yet incompletely understood. Large-scale trials have confirmed the induction of allergen-specific IgG antibodies to be dose dependent. There is no early suppression of allergen-specific IgE antibodies and a transient early increase in specific IgE antibodies as in SCIT.
Current models of SCIT propose the induction of antigen-specific Tregs (cell type in the body), which then orchestrate the observed antibody and mucosal changes observed during treatment. As of yet there is only scarce evidence that such mechanisms operate during SLIT. Comparative clinical studies of sublingual and subcutaneous treatment yielded heterogeneous results demonstrating efficacy of both modes, but SLIT to be a safer approach.
In conclusion, understanding of the interaction of allergen and antigen-presenting cells within the oral mucosa may allow improved targeting of SLIT vaccines. In the near future the combination of allergen products with adjuvants may improve efficacy of immunotherapy via the sublingual route.
So here’s the bottom line:
- Sublingual drops are not yet approved by the FDA and I can’t bill insurance for the product like allergists now do for subQ shots.
- Why not use Rapid immunotherapy to achieve maintenance in ONE month, followed by MONTHLY shots instead of weekly? With this method, you get the best of both worlds–good, proven benefits at a convenient dosing schedule.
- Sublingual drops have to be given multiple days per week and compliance isn’t all that impressive.
This issue isn’t going away, so stay tuned!